Chromatographic separations in the liquid and gas phase are commonplace and exploit a variety of molecular interactions. One general class of chromatographic interactions exploits only a single generalized property, such as interaction with an anion or cation or a hydrophobic stationary phase. Another general category, generally known as affinity chromatography, employs ligands that interact specifically with individual targets, such as antibodies or receptor proteins.
In the chromatographic mode employing ion-exchange supports or hydrophobic supports, the behavior of the molecules is generic with respect to groups--i.e., certain groups of molecules will be readily adsorbed to cation exchangers, others to anion exchangers, others to hydrophobic moieties and the like. These chromatographic techniques generally require large numbers of partitioning events to separate the individual members of these groups. On the other hand, in the "affinity" mode, only a very small class of molecules is adsorbed to the affinity support and all other molecules are unaffected. Thus, this latter method is unable to sort out individual members of large classes of compounds absent a multiplicity of individual steps involving individual affinity ligands.
Additional drawbacks of the foregoing conventional chromatographic methods reside in the difficulty of eluting the adsorbed materials in a biologically active form. Both the eluates from affinity chromatography using immunoglobulins, and those containing materials adsorbed to ion exchangers, show distortions in the molecular conformation of the contained materials (Ohlson, S. et al. Anal Biochem (1989) 169:204; Muller, W., J Chromatog (1990) 510:133).
The foregoing forms of chromatographic separations can be thought of as "single mode" procedures wherein only a particular property, such as charge, hydrophobicity, or specific affinity for a ligand is made the basis for separation. There has been limited experience with "mixed mode" sorbents where a number of features of the adsorbing moieties are employed. Such approaches are described in U.S. Pat. No. 4,694,044 wherein random copolymers of amino acids are used as a chromatographic matrix. Commercially available materials for the "mixed mode" approach include Polysorb MP3 (Interaction Chemicals), which is a polymeric sorbent containing both C-18 and sulfonic acid moieties. In addition, a series of Cibacron Blue dyes attached to DEAE or CM agarose are commercially available from Bio Rad.
PCT application WO 89/09088 describes, generally, the approach of using paralog sorbents for achieving mixed mode chromatography at a molecular level. As described in this publication, polymeric materials are constructed from individual monomer units in such a manner as to systematically vary at least two properties across the group of paralogs, thus providing a maximally diverse spectrum of affinities for a variety of target molecules. The present invention is directed to particular families of such paralogs which are designed to mimic, to systematically varying degrees, the properties of commonly used anion or cation exchange resins, such as diethylaminoethyl cellulose (DEAE) and carboxymethyl cellulose (CMC). These sorbents may be used as families to determine ideal supports for separation of particular mixtures, or singly for the actual separation of the members of these mixtures. In addition, these materials are helpful in selective elution of members of the groups of adsorbed molecules.